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Old 12-18-2008, 11:30 AM
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Pressure Testing fuel system

I finished plumbing and hanging all my fuel system goodies on my 70 Nova, and was curious how to go about pressure testing it? I was thinking I could cap off the hose that goes to the carburetor and then turn the pump on, and read the pressure rating at my fuel pressure gauge. What should I be checking for? Thanks!

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Old 12-18-2008, 01:26 PM
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Originally Posted by mrdreex
I finished plumbing and hanging all my fuel system goodies on my 70 Nova, and was curious how to go about pressure testing it? I was thinking I could cap off the hose that goes to the carburetor and then turn the pump on, and read the pressure rating at my fuel pressure gauge. What should I be checking for? Thanks!
You are going to need to set your regulator witht he motor running for best results but initially leave everything hooked up as it is and turn the fuel pump on and off just to cycle it. This should build enough pressure in the line to initially look for leaks. A tip prior to doing this is to fill the float bowls with fuel through the vent tube until the float comes up. This keeps from damaging the float when the electric pump is first turned on and the bowl would be otherwise empty. If after checking for leaks none are found you can then start the car and make adjustments. It's best to have a friend there with you to help watch and also have the proper fire extinquisher on hand.
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Old 12-18-2008, 01:38 PM
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Originally Posted by Tech @ BG
You are going to need to set your regulator witht he motor running for best results but initially leave everything hooked up as it is and turn the fuel pump on and off just to cycle it. This should build enough pressure in the line to initially look for leaks. A tip prior to doing this is to fill the float bowls with fuel through the vent tube until the float comes up. This keeps from damaging the float when the electric pump is first turned on and the bowl would be otherwise empty. If after checking for leaks none are found you can then start the car and make adjustments. It's best to have a friend there with you to help watch and also have the proper fire extinquisher on hand.
Thanks BG. Only problem here is that I haven't started the motor yet, nor is it in the car either. Is there a way to check for leaks without putting any fuel in it yet? Is calculating pressure bleed-off an accurate way of checking for leaks? I was thinking I could cap off the end of the hose with something, turn the pump on, read the pressure and see how long it takes for pressure to bleed out. Is this feasible?
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Old 12-18-2008, 01:46 PM
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Originally Posted by mrdreex
Thanks BG. Only problem here is that I haven't started the motor yet, nor is it in the car either. Is there a way to check for leaks without putting any fuel in it yet? Is calculating pressure bleed-off an accurate way of checking for leaks? I was thinking I could cap off the end of the hose with something, turn the pump on, read the pressure and see how long it takes for pressure to bleed out. Is this feasible?
Really no accurate way of measuring or even telling what the cause of the bleed of would be so we wouldn't advise that as a test. You can cycle the pump long enough to build pressure but it will deadhead the regulator with it capped off so just do it for a second or two but that does require having fuel in it. I have seen cars pull air into a fuel system and never leak yet cause a miss or skip too.
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Old 12-18-2008, 01:54 PM
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Originally Posted by Tech @ BG
Really no accurate way of measuring or even telling what the cause of the bleed of would be so we wouldn't advise that as a test. You can cycle the pump long enough to build pressure but it will deadhead the regulator with it capped off so just do it for a second or two but that does require having fuel in it. I have seen cars pull air into a fuel system and never leak yet cause a miss or skip too.
Looks like I'll have to wait until I can start it up before I can really look for leaks. Thanks BG.
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Old 12-18-2008, 02:04 PM
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Originally Posted by mrdreex
Looks like I'll have to wait until I can start it up before I can really look for leaks. Thanks BG.
You're welcome. Fuel can be a funny thing sometimes as I have seen cars that would not leak a drop while running but would after shutting them off while others would do the exact opposite. The one I mentioned in an ealier post was really hard to track down as it would only miss going through the lights and it turned out to be one of the teflon washers at the fuel cell bulhead leaking just enough air to affect the fuel supply but never leaked a drop.
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